Transporters are important in the production of amino acid and amino acid derived products because they transport compounds into and out of the cell, thereby influencing the intracellular concentration of these molecules. A high concentration inside the cell leads to feedback inhibition, which negatively affects production. For example, although feedback inhibition has been observed in lysC during lysine biosynthesis, feedback-resistant mutants were able to function in the presence of high concentrations of lysine (Kikuchi et al., FEMS Microbiology Letters 173:211-215, 1999; Ogawa-Miyata et al., Biosci. Biotechnol. Biochem. 65:1149-1154, 2001). Such feedback resistant mutants are able to generate higher lysine titers. Transport of molecules out of the cells can also reduce the effects of feedback inhibition.
Previous studies of the production of amino acids, such as lysine, and amino acid-derived products, such as cadaverine, focus on the overexpression or attenuation of genes involved in cellular metabolism. These modifications increase fluxes that lead to the production of the desired product, and decrease fluxes that lead to the production of side products or other metabolites not necessary for the formation of the desired product. However, additional methods of increasing the production of amino acids and their derived productions are needed.